1. Field of the Invention
This invention relates generally to a high-pressure, high-velocity, fluid-abrasive apparatus and, more particularly, to a fluid-abrasive nozzle adapted for use in such an apparatus.
2. Description of the Prior Art
At the present time, there are various abrasive-type blasting systems known which are used for removing painted or plastered surfaces. Many houses--particularly houses covered with a stucco material--after years of having several coatings of paint, must have these layers removed prior to providing a new coating of paint. Once the previous coatings of paint start to peel, they must all be removed and this is very often done by a sandblasting method.
Further, since the advent of a large number of private swimming pools, there has been created a need for providing a suitable apparatus or means to remove the first layer of plaster when it is found that the pool walls should be redone.
Most work of this type had been done by a method known as "dry-sandblasting" which is rapidly finding disfavor due to the emvironmental problems created by clouds of dust that are formed during the use of dry sand which is blown under high pressures.
Hence, in recent years the removal of unwanted materials or the need to change the physical characteristics of surface textures has brought forth combination wet and dry systems, these systems generally being referred to as "fluid-abrasive systems" wherein the fluid and various types of abrasives are intermingled and then discharged through a gun-like apparatus to obviate many of the above-mentioned problems.
However, this new method of mixing both a fluid and a dry abrasive also has created its own inherent problems. One problem is the wear on various parts. Another important problem is the inability to control the discharge patterns, since the effective pattern covered by most blasting systems is approximately two inches in diameter, which is not conducive to providing a smooth removal surface. A small pattern provides a poor distribution of abrasive within the pattern circle, thereby resulting in grooving and irregular blasting patterns, particularly on plaster surfaces.
Thus, it has been found that effectiveness of blast, blasting pattern, and nozzle characteristics of the known devices are extremely erratic. In addition, this problem did not vary directly with the different orifice sizes of a nozzle and, thus, could not be predicted. In fact, variations are found to be severe from nozzle to nozzle, even where each is provided with an identical-size orifice.
Further, the nozzles as employed in known systems require 10,000-12,000 p.s.i. pump-output pressure to accomplish effective surface erosion, resulting in frequent break-down periods of the equipment, and creating a shortened useable life and an increased safety hazard.
Since the present known nozzle has a single orifice, a very ineffective venturi effect is established, resulting in an inconsistent abrasive flow and difficulty in drawing the abrasive any appreciable distance, due to the lack of necessary vacuum in the abrasive line at the reservoir.
Accordingly, the applicant hereinafter discloses a unique fluid-abrasive nozzle that overcomes the foregoing mentioned problems.